Guide means permitting an exact motion of translation are required for variegated applications, in particular in the precision mechanics and electronic industries. For this purpose, there has been proposed in FR-PS No. 1 124 901 a rail whose head supports pairs of shafts on either side which are opposed by like pairs of shafts of a top carriage that is freely shiftable due to a plurality of balls between the neighboring pairs of shafts. However, considerable design effort is necessary to hold continuous series of balls tied along the entire rail. Relief came when the device according to GB-PS No. 1 081 669 was developed wherein a carriage is provided with linear ball bearings that run on shafts on either side of a rail body, riding on half the shait periphery and pressing the respective shaft onto a side groove in the rail body. Such arrangement, though, necessitates large tolerances; smooth running can easily be disturbed by maladjustment.
The guide system disclosed in DE-OS No. 30 40 711 employs two shafts supported on either side of a series of pillow blocks or pads. A carriage comprises pairs of rollers that run on the shafts at an obtuse angle to each other. The accuracy of the motion is determined by the exactitude with which the rollers are mounted in the carriage. Since the pillow blocks have to be introduced one by one in order to secure them on a support at given distances, the attachment of the rails is rather costly. Much the same holds for the use of clamping profiles that support the shaft along its length, exact fitting being of extreme importance. Another design as specified in EP-A No. 1-0 080 515 includes a rail support with a backing plate engaging the outer top of the shafts for pressing them towards the interior. Here it is, however, critical to fasten the bolts which pass through the individual pillow blocks, as the shafts may be slightly deformed.